Fast flexible electronics operating at radio frequencies (>1 GHz) are attractive because of their versatile capabilities, dramatic power savings when operating at reduced speed, and broad spectrum of applications, including applications in wireless and high-speed communications, remote sensing, and surveillance.
Transferrable single-crystalline Si nanomembranes (NMs) are useful materials for device layers in flexible electronics owing to their material uniformity, mechanical flexibility and durability, electrical properties, easy handling and processing, and low cost. While the carrier mobility of bulk Si can be enhanced using strain techniques, implementing these techniques into transferrable single-crystalline Si nanomembranes for fast flexible electronics has been challenging. In contrast to rigid devices fabricated from bulk Si, where strain in the active device layer can be easily sustained by a rigid substrate, the strain in free-standing transferrable Si nanomembranes needs to be self-sustained. A strain-sharing scheme between multiple epitaxial layers of Si and SiGe can self-sustain strain in transferrable nanomembrane structures and leads to enhanced electron mobility in Si. For truly high-speed device fabrication, however, doping of the Si nanomembrane is highly desirable. Unfortunately, the successful fabrication of doped, free-standing, strained Si nanomembranes has not yet been achieved.